The main ambition of this paper is to explain and analyze the difficult relations between China and Taiwan and its possible consequences for the regional and international security. The role of the United States is considered as a key actor. It permits to understand the strategies of the different actors due to the strong support given by Washington to Taiwan. The economic relations between the two neighbors are also interesting, to show how the topic is complex and sensitive. Our goal is to propose an analysis mentioning the ambitions of the different sides and their limits due to the realpolitik.